I also agree 100% on the bottlenecking issue. The 3800+ will certainly limit him on SLI. I would be very surprised if he is even getting his full potential from the single at this point. I would not expect to see much gain at all, if any.

The 939 limitation was the very reason I upgraded from my 3500+ to a new Rig. Costly yes but better than throwing good money after bad trying to achive performance enhancement that just wont happen.